python--公共字符串计算

import sys
while True:
    a = sys.stdin.readline().strip()
    if a == '':
        break
    b = sys.stdin.readline().strip()
    m = len(a)
    n = len(b)
    counter = [[0]*(n+1) for x in range(m+1)]
    # (m+1)个列表，每个列表含有(n+1）个元素
    longest = 0
    lcs_set = set() # 创建无顺序不重复的元素集
    for i in range(1, m+1):
        for j in range(1, n+1):
            if a[i-1] == b[j-1]:
                c = counter[i-1][j-1] + 1
                counter[i][j] = c
                if c > longest:
                    longest = c
                    lcs_set.add(a[i-c:i])
                elif c == longest:
                    lcs_set.add(a[i-c:i])
    max = 0
    for i in lcs_set:
        if len(i) > max :
            max = len(i)
    print(max)